The present invention relates generally to label applying apparatus such as those used in connection with food product weigh, wrap and label systems and, more particularly, to a vacuum actuated label applying wand.
In the label applying art the use of wands which pivot from a label pick-up station to a label applying station for transferring a label from the label pick-up station to the label applying station is known. The wand picks up a label from the pick-up station when a vacuum or partial vacuum is applied to the wand in order to attract the label to an opening at the end of the wand, which opening may be formed by a vacuum cup or other member. For example, U.S. Pat. Nos. 4,561,921, 4,787,953, 4,895,614, and 5,221,405, the specifications of which are hereby incorporated by reference, are representative of label applying mechanisms which utilize wands which are pivoted between label pick-up stations and label applying stations. Typically the label pick-up station is directly above the label applying station and the wand is pivoted to face the label pick-up opening upward for receiving a label from the label pick-up station. The wand is then pivoted to face the label pick-up opening downward at the label applying station where a stripper plate or head removes the label from the end of the wand and presses the label into contact with a package moving along a conveyor.
In such label applying systems positioning of the wand can be critical to achieve proper operation, particularly where the vacuum system used to attract the labels is not strong. For example, labels are typically delivered to the label pick-up station after being passed by a printer and removed from a roll of label stock. Labels near the inner end of the roll tend to curl when removed from the label stock due to the smaller radius of curvature near the inner end of the roll. When delivered to the label pick-up station the labels may curl upward. In this condition the labels do not present a planar surface which can be easily attracted by the label pick-up opening of the wand. Further, even where labels are not curved, limitations in the applied vacuum can make positioning of the wand critical and difficult. If the end of the wand is too high when it moves to the label pick-up station it may run into the edge of the label, but if the end of the wand is too low when it moves to the label pick-up station it may not be close enough to attract the label properly. In such situations significant time may be spent adjusting the position of the wand to achieve suitable operation.
Accordingly, it would be desirable to provide a wand which enables suitable label pick-up without requiring significant and timely adjustments.
As used herein the term xe2x80x9cvacuumxe2x80x9d is intended to broadly encompass partial vacuums as well as full vacuums.
In one aspect of the present invention, a label applying apparatus is formed by a wand assembly including a first portion having a vacuum opening for connection to a vacuum source, and a second portion movable relative to the first portion along an axis of the wand assembly to define at least a non-extended position and an extended position. A first chamber is defined between the first portion and the second portion, the first chamber in fluid communication with the vacuum opening. A second chamber is spaced from the first chamber, the second chamber in fluid communication with ambient atmosphere. A sealing member is provided between the first chamber and the second chamber. Application of a vacuum to the vacuum opening creates a low pressure condition in the first chamber which causes the second portion to move axially away from the first portion in order to reduce the size of the first chamber, the movement of the second portion placing the wand assembly in the extended position. In application, the wand assembly can be maintained in the non-extended position in order to assure the end of the wand assembly does not run into the edge of a label during movement toward the label pick-up station, and the wand assembly can then be placed in the extended position to assure a label pick-up opening of the wand assembly is close enough to the label to properly attract it.
In another aspect of the invention, a label applying apparatus is formed by a wand assembly including a first portion having a vacuum opening for connection to a vacuum source, and a second portion movable relative to the first portion along an axis of the wand assembly to define at least a non-extended position and an extended position. A biasing member is provided for urging the wand assembly into the non-extended position. The second portion includes a label pick-up opening at an end thereof. Application of a vacuum to the vacuum opening of the first portion causes the wand assembly to be placed in the extended position and termination of the vacuum causes the wand assembly to return to the non-extended position.
Still another aspect of the invention provides a method for transferring a label to a label applying station for application to a package traveling along a conveyor which involves (a) providing a vacuum actuated wand assembly including a first portion and a second portion movable relative to each other to define an extended position and a non-extended position of the wand assembly, the wand assembly movable between the non-extended position and the extended position when a vacuum is applied to a passage of the first portion, the first portion connected to a wand assembly pivoting location, a label pick-up opening positioned at an end of the second portion and in fluid communication with the vacuum source when the wand assembly is in the extended position; (b) pivoting the wand assembly toward the label-pick-up station while in the non-extended position; (c) applying a vacuum to the wand assembly when the label pick-up opening reaches a defined position, the vacuum placing the wand assembly in the extended position and attracting the label to the label pick-up opening; and (d) pivoting the wand assembly toward the label applying station.